Hold down mechanism for printing plate processor

ABSTRACT

A hold-down mechanism for a printing plate processor divided into a lower fixed section and an upper pivotal section along a plane coincident with the path of travel of the plate therethrough, latch means pivotally mounted on the lower section, hydraulic cylinder means operatively connected to the latch means for pivoting the latch means into and out of locking engagement with the upper section, and pressurized fluid supply means for supplying pressurized processing fluid to the hydraulic cylinder means.

United States Patent 1 Schichlein 1 June 12, 1973 HOLD DOWN MECHANISM FOR PRINTING PLATE PROCESSOR [75] Inventor: Burghard K. Schichlein, Gillette,

NJ. [73] Assignee: Azoplate Corporation, Murray Hill,

[22] Filed: Oct. 21, 1971 21 Appl. No.2 191,190

[52] U.S. Cl. 95/89 R, 95/94 R, 49/279 [Sl] Int. Cl. G03d 3/00 [58] Field of Search 95/89 R, 94; 49/279,

[56] References Cited UNITED STATES PATENTS 3,440,944 4/1969 Endermann et al 95/89 R 3,272,552 9/1966 Park 49/280 X 8/1965 Weinstein 49/379 3/1956 Bayley 49/280 X Primary Examiner-John M. l-loran Assistant Examiner-Richard M. Sheer Attorney-James E. Bryan {57] ABSTRACT 5 Claims, 1 Drawing Figure ,DEVELOPER LINE T0 DEVELOPER SECTION PATENIEU 1 2 3. 738 249 ilu n fi l INVENTOR BURGHARD K. SCHICHLEIN WXA M ATTORNEY HOLD DOWN MECHANISM FOR PRINTING PLATE PROCESSOR This invention relates to an apparatus for processing printing plates and, more particularly, to an apparatus for holding two sections of a printing plate processing apparatus in closed relationship.

Conventional offset printing plates usually comprise a thin sheet of aluminum coated with a light-sensitive layer which contains, among other things, one or more resins. Such sensitized printing plates may be made ready for printing by the platemaker by various manual techniques. For example, the platemaker either purchases the raw aluminum and then treats it in various fashions, known to the industry, to prepare it for coating with one of several commercially available lightsensitive emulsions, or he purchases the aluminum pre pared for such coating. The coatings are then applied to the aluminum carrier in one of several known ways and the coating is then dried. These presensitized plates are then ready for use in printing by the printer. Alternately, the platemaker may purchase a preprepared, precoated plate conventionally known as a presensitized offset printing plate.

The presensitized offset printing plate is thereafter exposed, through a stencil, to a source of strong actinic light, for example, a carbon arc. The light-sensitive coating, when subjected to such light, is converted in such a manner that, after development, the image areas are retained on the plate surface and the non-image areas are removed or vice versa.

It is also known in the lithographic industry that the exposed printing plate may then be developed by what is known as the hand developing process. In this process, the plate is first rubbed with a sponge or the like saturated with a developing agent to rub the developing agent into the surface of the plate. The plate may be fixed and/or washed and finally, a coating of material, such as gum arabic, is applied to the surface of the plate to protect the image-free areas. The plate is then ready for the printing press.

More specifically, this hand-developing process for producing aprinting plate involves the following procedure: From a typewritten setup or makeup, equivalent to the material to be printed and provided in any desired manner, including typed articles, pictures of various kinds of art work of different sizes, and the like, all assembled onto a suitable cardboard or other support, a master is prepared in the conventional manner. The image of the master is then transferred onto the sensitized printing plate, as previously described, by a suitable exposure technique.

The printing member thus'prepared is then subjected to a developing operation utilizing the chemistry prescribed by the manufacturer of the printing plate. This chemistry is worked into the exposed coating by hand-rubbing, for example, with a sponge, until the non-image areas are subtracted or removed from the carrier leaving an exact replica of the image on the plate carrier. Obviously, in the alternate process, the image areas may be removed leaving the non-image areas on the carrier plate. The printing member is then fixed and/or washed and a solution of gum arabic or a similar solution, is applied to the plate surface, resulting in a printing plate which is ready for the printing press.

There are numerous disadvantages to this handprocessing of offset printing plates. First of all, the process is slow and expensive. In addition, it is almost impossible to uniformly apply the chemistry to remove the undersired coating and uneven exposure to the chemistry" is attained. Therefore, defective printing often results from an inadequate development or underdevelopment of an area or from applying varying pressure by hand which may adversely affect the desired printing image. Drying of the developer on certain portions of the plate before it can be rubbed in, to remove the undesired coating, also may leave a residue on the plate.

In order to overcome the difficulties of hand processing and to speed up the process, a variety of automatic and semiautomatic processing equipment is now available. Some of this equipment is built in such a fashion that the plate is turned around during processing and returned to the operators side of the machine. Other equipment has also been designed for straight throughput so that the equipment can be installed in in-line systems.

While this automatic and semiautomatic equipment has been an improvement, it is also subject to the inherent problem of lack of accessibility. In the operation of processing equipment of this type, the equipment necessarily becomes dirty and contaminated through use and, therefore, must be cleaned periodically. In present day automatic and semiautomatic processing equipment, such cleaning is a major undertaking. Another problem inherent in present commercially available equipment is that the plates become jammed in the equipment at times and have to be removed. Such jamming may result if the edges of the thin metal plates are inadvertently bent over or the plate has an undesirable curve or bulge. This will cause the plate to mistrack in the apparatus and thus, become jammed. It is also possible to inadvertently insert the plate askew in the machine so that it will not follow its normal path or will run sidewise in the machine and thus, become lodged or jammed.

While the apparatus of the present invention is applicable to any of a variety of printing plate processing apparati, and particularly to printing plate developing apparatus where developing fluid is supplied to the apparatus under pressure, the invention is best adapted for use in conjunction with a processing apparatus in which the plate travels in a straight line path through the machine, starting with an exposed plate and ending with a dried plate ready for use by the printer. Such processing apparatus generically includes a developing section, which is supplied with a developing fluid under pressure, a washing section, a lacquering or gunning section and adrying section. The developer section generally includes a pre-soak station, in which developer fluid is sprayed under pressure onto the exposed surface of the plate in order to develop the plate and permit removed coating to flow free of the plate, a cleaning section where moving brushes and additional developer spray clean the surface of residual unwanted portions of the coating, and a scrubbing section where moving pads, supplied with additional developing fluid under pressure, remove the last traces of unwanted coating from the plate. After passing through the developing section, a second or third application of developing fluid may be applied if required. Following the developing section may be a similar section where a fixing solution is applied to the plate. The plate then enters a washing section where it is washed free of any residual developing and fixing fluids. From the washing section, the plate then passes to a lacquering or gumming section where a protective coating, such as gum arabic, is applied. Finally, the plate passes to a drying section where the plate is dried and discharged as a completed plate ready for the printing press.

In accordance with the present invention, processing apparatus of the character described above, or any one or more components thereof, is divided into a lower fixed section and an upper pivotal section along a plane parallel to the path of the plate member passing through the apparatus. Where such printing plate processing apparatus is thus divided into an upper and a lower section and the upper section is pivotally connected to the lower section, it is necessary that the operating units, that is, the top and bottom sections of the processing apparatus, be held in a precise position relative to one another and that any movement of the top and bottom sections relative to one another during the operation of the unit be avoided. One way of properly positioning the two sections of the apparatus and attaining a good locking relationship between the .two is by employing screw-type jacks to open and close the top. However, on very large processing apparatus capable of continuously processing plates of about 45 inches and wider, which are normally also heavier in gage, additional means for holding the two sections in their closed position is often desirable. Such additional holddown or latching means becomes even more of a necessity when the processing apparatus includes components which are moving in a direction transverse to the movement of the plate.

The present invention therefore provides a simple and positive means for latching the two sections of the processing apparatus together during operation. By positively locking the two sections together during operation, accidental opening by the operator is avoided while the machine is in operation and possible accidents are prevented.

Specifically, in accordance with the present invention, an exposed printing plate is fed into the machine for processing. The plate actuates an electrical limit switch which, in turn, supplies power to the driven rollers of the processing apparatus which feed the plate through the processing apparatus. Simultaneously with the supply of power to driven rollers, power is supplied to the developer fluid pump which supplies the developer fluid to the developing section of the processing apparatus. The developer pump is thus started immediately and operates at a hydraulic pressure of approximately 50 psi. By appropriately bleeding off or bypassing a part of the developer fluid under pressure, this fluid may be utilized to actuate a small hydraulic cylinder assembly. The hydraulic cylinder assembly is, in turn, attached to an appropriate latch means. The latch means is pivoted adjacent its center on the lower stationery section of the processing equipment, the piston rod of the piston cylinder assembly is pivotally attached to the lower end of the latch means and the cylinder body is pivotally attached to this same stationery lower section of the apparatus. As the piston rod is extended under influence of the hydraulic pressure in the hydraulic cylinder assembly, it causes the latching mechanism to rotate about its pivot and a slot in the upper end of the latching means locks onto a stud fixedly attached to the upper pivoted section of the processing apparatus. Thus, the upper pivoted section of the processing apparatus is securely locked to the lower stationery section of the processing apparatus the instant the machine is put into operation. When the machine completes its operation or is turned off, the hydraulic pressure is reduced to 0, and a spring return of the hydraulic cylinder assembly retracts the piston and thereby unlocks the upper pivotal section of the machine from the stationery lower section. Consequently, the machine can now be opened, if desired, for

inspection, service or the like.

In accordance with the drawing, the processing apparatus is mounted on a base comprising legs 2 and 4 and cross support 6. The lower section 8 of the processing apparatus is fixedly mounted on top of legs 2 and 4 and an upper section 10 is pivotally mounted to lower section 8 through fixed support plates 12 and pivot means 14 mounted in the sections of plates 12 which extend above the lower section 8. Operatively mounted within lower section 8 of the processing apparatus are driven rollers 16 which transport the plate through the processing apparatus. Mounted in the upper section 10 of the processing apparatus are idler rollers 18 which are in intimate contact with the plate passing through the processing apparatus and are therefore driven by such contact with the plate being processed.

Mounted on cross member 6 of the frame of the apparatus is a developer fluid reservoir 20. Developer fluid is drawn from reservoir 20 through line 22 by means of developer fluid pump 24. Developer fluid pump 24 then forces the developer fluid through line 26 under pressure. Developer fluid line 26 is connected to a conventional T-joint 28. From T-joint 28, branch line 30 carries developer fluid to the developer section (not shown) of the processing apparatus. Also, leading from T-joint 28 is branch line 32 which carries developer fluid to a small hydraulic cylinder assembly, generally designated as 34. The hydraulic cylinder assembly 34 consists of a conventional cylinder 36 to receive pressurized fluid from branch line 32, a piston (not shown) disposed in cylinder 36 and a piston rod 38 connected to the piston. The piston is also provided with a conventional return spring (not shown). The cylinder 36 of hydraulicpiston assembly 34 is pivotally mounted on the lower section 8 of the processing apparatus through pivot means 40. Also mounted on lower section 8 of the processing apparatus is a latch means of arm 42. Latch means 42 is pivotally mounted adjacent its center through pivot means 44. The free end of piston rod 38 is pivotally connected to the lower end of latch means 42 through pivot means 46. Mounted on the upper section 10 of the processing apparatus is a latching or holddown stud 48. Holdlatching stud 48 cooperativelyengages slot 50 formed in the upper end of latching arm 42.

In operation, when the exposed printing plate is fed into the processing apparatus, the plate contacts a limit switch 52. Limit switch 52 supplies electrical power to the processing apparatus, including, power to the driven rollers 16 and the developer fluid pump 24. The developer fluid pump causes fluid pressure to build up in lines 26, 30 and 32. The fluid pressure through line 32 actuates the piston of the hydraulic cylinder assembly 34 to extend piston rod 38. As the piston rod 38 is extended, it, in turn, pivots the latchingarm 42, thereby locking the upper section 10 of the processing apparatus to the lower section 8. As a result, the upper section of the processing apparatus is securely locked to the lower section 8 the instant the machine is put into operation. When the processing apparatus completes its operation, it is either manually or automatically turned off thus, resulting in a reduction of the fluid pressure in the developer fluid lines 26, 30 and 32. The piston is then retracted by means of the spring return mounted in the cylinder 36, thereby unlocking the upper section 10 of the processing apparatus so that the machine can now be opened if desired for inspection, service or the like.

Obviously, the holddown arm 42 can be automatically actuated by means other than the hydraulic cylinder. For example, a solenoid operated mechanism could be utilized which would be operative when the limit switch 52 turns on the power. However, such solenoid operated mechanisms are both expensive and much more complicated than the hydraulic system of the present apparatus. The hydraulic system of the present apparatus, therefore, has the additional advantage of being highly reliable, reasonable in cost and utilizes fluid pressure which is readily available as a result of the operation of the developer section of the processing apparatus.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

What is claimed is:

1. In a printing plate processor having a lower fixed section and an upper pivotal section, divided along a plane coincident with the path of travel of a printing plate therethrough, and a processing fluid source; the improvement, comprising, latch means mounted on one of said sections for releasably holding said upper section in a closed position against said lower section; hydraulic cylinder means, operatively connected to said latch means for moving said latch means into and out of holding engagement with that one of said sections which does not carry said latch means; and pressurized fluid supply means for supplying pressurized processing fluid from said processing fluid source to said hydraulic cylinder means.

2. In a printing plate processor in accordance with claim 1 wherein the latch means comprises a latching arm pivotally mounted on the lower section of the processor and having a notch formed adjacent its upper end and a latching stud mounted on the upper section of the processor for engaging said notch of said latching arm.

3. In a printing plate processor in accordance with claim 2 wherein the hydraulic cylinder means is pivotally mounted on the lower section of the processor and a rod of said hydraulic cylinder means is pivotally connected to the latching arm.

4. In a printing plate processor in accordance with claim 1 wherein the processing fluid is printing plate developer fluid.

5. In a printing plate processor in accordance with claim 1 wherein the pressurized fluid supply means is a pump for supplying processing fluid to both the processor and the hydraulic cylinder means. 

1. In a printing plate processor having a lower fixed section and an upper pivotal section, divided along a plane coincident with the path of travel of a printing plate therethrough, and a processing fluid source; the improvement, comprising, latch means mounted on one of said sections for releasably holding said upper section in a closed position against said lower section; hydraulic cylinder means, operatively connected to said latch means for moving said latch means into and out of holding engagement with that one of said sections which does not carry said latch means; and pressurized fluid supply means for supplying pressurized processing fluid from said processing fluid source to said hydraulic cylinder means.
 2. In a printing plate processor in accordance with claim 1 wherein the latch means comprises a latching arm pivotally mounted on the lower section of the processor and having a notch formed adjacent its upper end and a latching stud mounted on the upper section of the processor for engaging said notch of said latching arm.
 3. In a printing plate processor in accordance with claim 2 wherein the hydraulic cylinder means is pivotally mounted on the lower section of the processor and a rod of said hydraulic cylinder means is pivotally connected to the latching arm.
 4. In a printing plate processor in accordance with claim 1 wherein the processing fluid is printing plate developer fluid.
 5. In a printing plate processor in accordance with claim 1 wherein the pressurized fluid supply means is a pump for supplying processing fluid to both the processor and the hydraulic cylinder means. 